Go ahead and use the ego battery with the dual coils. I do it all the time. They will not last as long between charges as you are drawing more current but other than not being recommended, as long as the battery will fire it go ahead and use it. The one draw back is that like the 510 mega battery the voltage is regulated so what you get is all your going to get out of it =] You will probably shorten the usable life of the battery because of the extra stress you are putting on it but what the heck.
You will ultimately want a variable voltage device so you can dial in the voltage that works best for the carto you have attached. I can't personally recommend a VV as I built mine myself. However I have heard nothing but good about the Darwin, except $$$$$$$$$$$$.... If I would have spent the $$$$$$$$$ on a Darwin to begin with I wouldn't be over $500 bucks into the hobby in two months. Of course I wouldn't have had as much fun either =]
With the ego batt that is missing the switch you might be able to just find something that will fit down inside the opening to replace the button top. I'm thinking if you have a sewing box you could find something that you could set in there to be able to push the switch. I'm thinking of something like one of those little stick on jewels. As long as the switch still functions all you need is something that you can push on to activate it. If you find something just put a tiny drop of hot glue on it and stick in. Just be careful not to put too much on as it can glue the switch itself into position if your not careful. You can just use the tip of a pen to see if the switch still works or not.
You will ultimately want a variable voltage device so you can dial in the voltage that works best for the carto you have attached. I can't personally recommend a VV as I built mine myself. However I have heard nothing but good about the Darwin, except $$$$$$$$$$$$.... If I would have spent the $$$$$$$$$ on a Darwin to begin with I wouldn't be over $500 bucks into the hobby in two months. Of course I wouldn't have had as much fun either =]
With the ego batt that is missing the switch you might be able to just find something that will fit down inside the opening to replace the button top. I'm thinking if you have a sewing box you could find something that you could set in there to be able to push the switch. I'm thinking of something like one of those little stick on jewels. As long as the switch still functions all you need is something that you can push on to activate it. If you find something just put a tiny drop of hot glue on it and stick in. Just be careful not to put too much on as it can glue the switch itself into position if your not careful. You can just use the tip of a pen to see if the switch still works or not.